Development of a Scalable Process for the Synthesis of Red Base RC

5-Chloro-2-methoxyaniline hydrochloride, commonly known as Red Base RC, is a widely utilized intermediate in the dye and pigment industry for colorant synthesis. Its precursor, 5-chloro-2-methoxyaniline, also exhibits significant utility in pharmaceutical and material science applications. Conventional synthetic methods typically involve harsh reaction conditions and hazardous nitration processes, and posing notable environmental concerns. In this work, a three-step synthetic route starting from 4-chlorophenol was developed for the preparation of Red Base RC without the need for chromatographic purification. The strategy comprises an efficient diazo coupling reaction to form an azo intermediate, followed by catalytic hydrogenation and selective O-methylation using dimethyl carbonate as a green methylation agent. This process employs commercially available and inexpensive starting materials, enables simple operation, delivers high product purity, and achieves a total yield exceeding 65%, demonstrating strong potential for industrial scale-up. As such, it represents a highly efficient and sustainable synthetic pathway for this class of key intermediates.